Digital communication techniques have effectively revolutionized the communications industry by creating efficiencies in bandwidth utilization previously not possible using older analog methods. Information can now generally be conveyed more accurately at higher rates within a smaller bandwidth of a given communications medium. Where spectrum is shared through segmentation of the medium into channels, these efficiencies can permit a higher number of channels through narrower channel widths closer channel spacing than with analog techniques. Digital communication systems generally have superior noise rejection characteristics compared to their analog counterparts, yet care is still taken in their design to avoid cross channel noise that exceeds permissible thresholds. Whether bandwidth is shared across a number of entities, as in the case of government assigned airspace, or commonly owned, as in the case of a coaxial cable of a television service provider, reduction or prevention of cross channel noise can avoid potential regulatory issues, reliability problems, and customer complaints.
Digital communication methods generally include the use of an analog carrier signal that is modulated using digital data. The analog carrier permits the digital data to be transmitted in a given frequency range (i.e., a channel) without interfering with signals being transmitted on other frequencies. During normal operation, the output of a given modulation circuit is generally confined to its assigned frequencies. During a transient event, however, such as power being removed or initially supplied, components of the modulation circuitry can receive and/or output unintended signals that cause the ultimate output of the modulator circuit to include frequencies well outside its intended frequency range. This results in unacceptable broadband noise that can have a detrimental effect on other channels in the communication medium.